text: In fluid dynamics, a Stewartson layer is a thin cylindrical shear layer that connects two differentially rotating regions in the radial direction, namely the inside and outside the cylinder. The Stewartson layer, typically, also connects different Ekman boundary layers in the axial direction. The layer was first identified by Ian Proudman and was first described by Keith Stewartson.  This layer should be compared with the Ekman layer which occurs near solid boundaries.